首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   2831篇
  免费   185篇
  国内免费   13篇
耳鼻咽喉   57篇
儿科学   60篇
妇产科学   95篇
基础医学   362篇
口腔科学   22篇
临床医学   250篇
内科学   594篇
皮肤病学   79篇
神经病学   237篇
特种医学   147篇
外科学   402篇
综合类   53篇
预防医学   220篇
眼科学   22篇
药学   210篇
中国医学   1篇
肿瘤学   218篇
  2023年   14篇
  2022年   24篇
  2021年   39篇
  2020年   43篇
  2019年   57篇
  2018年   65篇
  2017年   53篇
  2016年   52篇
  2015年   50篇
  2014年   75篇
  2013年   126篇
  2012年   126篇
  2011年   128篇
  2010年   107篇
  2009年   96篇
  2008年   113篇
  2007年   113篇
  2006年   127篇
  2005年   105篇
  2004年   119篇
  2003年   84篇
  2002年   64篇
  2001年   86篇
  2000年   83篇
  1999年   72篇
  1998年   54篇
  1997年   39篇
  1996年   44篇
  1995年   48篇
  1994年   42篇
  1993年   40篇
  1992年   66篇
  1991年   52篇
  1990年   46篇
  1989年   54篇
  1988年   43篇
  1987年   45篇
  1986年   51篇
  1985年   45篇
  1984年   36篇
  1983年   39篇
  1982年   21篇
  1981年   30篇
  1980年   17篇
  1979年   18篇
  1978年   31篇
  1977年   23篇
  1975年   16篇
  1974年   28篇
  1967年   11篇
排序方式: 共有3029条查询结果,搜索用时 15 毫秒
21.
Summary 20 male elite long distance runners were compared to a control group of blood donors to determine the effect of training on red blood cells. The acute effects of exercise on red cells were investigated in 11 of the runners following a race of 15–30 km. The runners had elevated resting values of red cell 2,3-DPG (P<0.05) and mean cell volume (P<0.01); blood Hb and ATP were not different from concentrations in the control group. The red cell status of the athletes may be explained by an increased proportion of young erythrocytes in runners. No statistically significant changes in red cell 2,3-DPG, ATP, mean cell volume or blood Hb were found post exercise.  相似文献   
22.
23.
Children with recurrent lower respiratory tract infection (RLRI) may respond poorly to polysaccharide antigens. To examine how such children respond to a polysaccharide coupled to a protein carrier, we immunized 15 children with RLRI aged 8–69 months and 15 carefully age-matched healthy controls once with a Haemophilus influenzae type b (Hib) conjugate vaccine. Total IgG subclasses, total antipolysaccharide Hib antibodies, and antipolysaccharide Hib antibodies of IgM, IgG, IgA, and IgG 1–4 specificity were determined by ELISA. There were no significant differences between the two groups in any single total IgG subclass, but total IgG measured as the sum of all four subclasses was significantly lower in the children with RLRI than in the controls ( P = 0.036). Before vaccination, the children with RLRI had significantly less IgG antipolysaccharide Hib antibody than the controls ( P = 0.005), whereas 1 month later they had significantly more IgM antibody (P = 0.038). No other significant differences were found between the groups before or after immunization with respect to antipolysaccharide Hib antibodies. Since naturally occurring IgG antibodies are thought to be aquired partly as a consequence of antigenic stimulation on mucosal surfaces, we hypothesize that the low level of specific IgG found before immunization, as well as the low total IgG in the children with RLRI, may reflect an impaired ability to prime through mucosal surfaces. This is supported by our finding of an increased IgM response to Hib conjugate vaccine in these children, since this isotype predominates in the primary immune response, i.e., in the absence of immunologic memory. In conclusion, children with RLRI can be protected against invasive Hib infection as well as healthy children, but may have an immunodeficiency characterized by defective ability to respond to antigenic stimulation on mucosal surfaces.  相似文献   
24.
25.
26.
Alpers'' disease     
Observations on skin reflectance were made on 309 endogamous Indian families, for constitutive (medial upper arm) and facultative skin colour (forehead) to investigate which of the two colours is under a rigid control of genetic action. An assessment of data by coefficient of correlation "r" show that facultative colour is inherited more strictly than the constitutive colour.
Received 4 July, accepted 3 October 1983  相似文献   
27.
PIK3CA belongs to the phosphatidylinositol 3-kinases (PI3Ks) family, which play an important role in proliferation, adherence, transformation and cell survival through the PI3K/AKT signaling pathway. Somatic activating mutations of this gene have recently been detected in several types of cancers. In the present study, 109 advanced ovarian carcinomas were analyzed for PIK3CA mutations in exon 9 and exon 20 by direct sequencing. Activating missense mutations were observed in 4 of the 109 tumors in addition to one variant leading no change of the PIK3CA protein. Two of the cases with mutations were mucinous and clear cell tumors, suggesting that PIK3CA mutations are more common in these rare histological types.  相似文献   
28.
The HLA-D/DR region in man encodes major determinants which stimulate T lymphocytes to proliferation. The genetic organization of this region is apparently complex and is at present largely unknown. One obstacle is the scarcity and quality of available typing reagents. In an attempt to obtain high quality anti-DR sera, a series of active immunizations was performed between highly selected, healthy unrelated donors and recipients.
One recipient (AR8) was immunized using cells incompatible for HLA-A2, B40 (w60), Cw3 and DIDRw6 and readily developed anti-A2 and B40 antibodies but no anti-C, DR, or other antibodies. When tested against his HLA genotypically fully identical brother using the cellular MLC, PLT, or CML techniques before immunization, results were mutually negative as expected. Following immunization, however, AR8 was able to mount MLC, PLT, and possibly CML responses against lymphocytes from the brother while the reverse combinations remained negative. When tested in the family the trait(s) thus identified seems to be maternally inherited.
These results suggest the existence of minor histocompatibility determinants encoded from regions not closely linked to HLA. The brother of AR8 and the immunizing donor thus seem to share one or more determinants not possessed by AR8.  相似文献   
29.
Summary In 23 patients with rheumatoid arthritis the plasma protein binding of3H-imipramine and the plasma levels of 13 proteins were measured in order to examine the significance of the proteins for the binding of imipramine. The degree of3H-imipramine binding did not differ significantly from that in healthy controls. It was positively correlated with the concentrations of fibrinogen, 1-acid-glycoprotein, ceruloplasmin, complement C3c, haptoglobin and hemopexin. Erythrocyte sedimentation rate was also highly positively correlated with binding. The concentration of several of the proteins showed a significant covariation. The3H-imipramine binding was negatively correlated with the concentration of albumin and the latter was negatively correlated with some of the proteins mentioned-above. No correlation with the levels of apolipoproteins A and B was found. There appears to be more a qualitative than a quantitative change in3H-imipramine binding in patients with rheumatoid arthritis.  相似文献   
30.
Acute porphyria is rare in orientals. We describe a Chinese woman with recurrent generalised tonic-clonic seizures and abdominal pain. Genomic DNA studies identified a heterozygous base substitution from guanine to adenine at nucleotide position 503, resulting in substitution of arginine by histidine at position 168 of the protein (R168H). This genetic abnormality is similar to the mutation reported in Caucasians with variegate porphyria. To the best of our knowledge, this is the first report in the English literature a Chinese patient with variegate porphyria with an identifiable mutation. A brief review of porphyria is presented.  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号